Alternator temperature in enclosed engine bay

[Seamaster_IRL]

Hi All, I am running twin alternators off a raw water cooled Perkins 4.236 running around 84C. I am starting to build a fully enclosed engine bay for sound and wanted advice on whether or not the alternators would require external mounting due to heat. They can take 120C max. What experienced advice can you offer? Appreciate the inputs...

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[DeepFrz]

Every engine bay should be ventilated. The engine needs fresh air and will run better on cooler air. Make sure the inlet and outlet vents are outside with the inlet vent low in the engine room and the outlet vent high in the engine room. Often there is an exhaust fan on the outlet vent so the inlet vent needs to be larger in size in order to supply enough cool air for cooling the engine room and for combustion air. A fan or vent hose directed at an alternator can help keep it cool. Engine room temperature should not exceed 125 deg f or 52 deg. c.

[Seamaster_IRL]

@DeepFrz. Thanks for the advice. Much appreciated

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[Flyfisher69]

I'm new to posting on a forum, so I'm hoping that I'm not stepping on anybody's post. I have a Morgan sail boat, and it has an in and out vent high in the engine room. The inline blower just went and I was thinking of putting and inline fan on both the in and out vent. In side vent tubing low and the out tubing high in the engine room to vent the engine compartment heat. Do you think this will be better than one inline vent blower? Thanks

[GordMay]

Greetings and welcome aboard the CF, Flyfisher.

Yes.

[Dockhead]

Originally Posted by DeepFrz

Every engine bay should be ventilated. The engine needs fresh air and will run better on cooler air. Make sure the inlet and outlet vents are outside with the inlet vent low in the engine room and the outlet vent high in the engine room. Often there is an exhaust fan on the outlet vent so the inlet vent needs to be larger in size in order to supply enough cool air for cooling the engine room and for combustion air. A fan or vent hose directed at an alternator can help keep it cool. Engine room temperature should not exceed 125 deg f or 52 deg. c.

That's all very good advice.

Not only your alternator, but your engine, and just about everything else in your engine space, needs plenty of cool, fresh air. Ventilation is paramount. Your engine will have less power and run less efficiently if you don't feed it cool air, and alternators and other such equipment won't be as efficient and won't last as long if you don't keep them cool.

Besides what DeepFrz recommends, I would suggest a temperature sensor in the engine space to keep an eye on the ambient temperature in there.

[GordMay]

Several previous discussions ➥ engine ventilation gordmay - Google Search

[rourkeh]

Just read this post. A much more important concern for you if you are creating an enclosed engine space should be the effect of the high temperature on the main engine. one of the #1 reasons for the failure of sailboat auxiliary engines is high temperature environment. Small displacement, non turbo charged diesel engines should last the life of the boat. Yet most sailboat diesels are lucky to last a few thousand hours.
There is a good article here Marine Engines: Sail Boat Auxiliaries at Dockside Reports
that you should read before baking both your alternators and your main engine.

[Dockhead]

Originally Posted by rourkeh

Just read this post. A much more important concern for you if you are creating an enclosed engine space should be the effect of the high temperature on the main engine. one of the #1 reasons for the failure of sailboat auxiliary engines is high temperature environment. Small displacement, non turbo charged diesel engines should last the life of the boat. Yet most sailboat diesels are lucky to last a few thousand hours.
There is a good article here Marine Engines: Sail Boat Auxiliaries at Dockside Reports
that you should read before baking both your alternators and your main engine.

Nothing against the idea of ensuring copious ventilation to your engine space (an idea which I support), but I would take all of these articles by David Pascoe with a grain, no, a whole box of salt. This is a highly opinionated person who has written hundreds of pages on subjects like -- never buy a Yanmar engine since they have aluminum parts and must fail, never buy a boat with a cored hull, etc., etc., etc., etc.